Textile properties of synthetic prolapse mesh in response to uniaxial loading

Abstract

BACKGROUND Although synthetic mesh is associated with superior anatomic outcomes for the repair of pelvic organ prolapse, the benefits of mesh have been questioned because of the relatively high complication rates. To date, the mechanisms that result in such complications are poorly understood, yet the textile characteristics of mesh products are believed to play an important role. Interestingly, the pore diameter of synthetic mesh has been shown to impact the host response after hernia repair greatly, and such findings have served as design criteria for prolapse meshes, with larger pores viewed as more favorable. Although pore size and porosity are well-characterized before implantation, the changes in these textile properties after implantation are unclear; the application of mechanical forces has the potential to greatly alter pore geometries in vivo. Understanding the impact of mechanical loading on the textile properties of mesh is essential for the development of more effective devices for prolapse repair. OBJECTIVE The objective of this study was to determine the effect of tensile loading and pore orientation on mesh porosity and pore dimensions. STUDY DESIGN In this study, the porosity and pore diameter of 4 currently available prolapse meshes were examined in response to uniaxial tensile loads of 0.1, 5, and 10 N while mimicking clinical loading conditions. The textile properties were compared with those observed for the unloaded mesh. Meshes included Gynemesh PS (Ethicon, Somerville, NJ), UltraPro (Artisyn; Ethicon), Restorelle (Coloplast, Minneapolis, MN), and Alyte Y-mesh (Bard, Covington, GA). In addition to the various pore geometries, 3 orientations of Restorelle (0-, 5-, 45-degree offset) and 2 orientations of UltraPro (0-, 90-degree offset) were examined. RESULTS In response to uniaxial loading, both porosity and pore diameter dramatically decreased for most mesh products. The application of 5 N led to reductions in porosity for nearly all groups, with values decreasing by as much as 87% (P < .05). On loading to 10 N of force, nearly all mesh products that were tested were found to have porosities that approached 0% and 0 pores with diameters >1 mm. CONCLUSION In this study, it was shown that the pore size of current prolapse meshes dramatically decreases in response to mechanical loading. These findings suggest that prolapse meshes, which are more likely to experience tensile forces in vivo relative to hernia repair meshes, have pores that are unfavorable for tissue integration after surgical tensioning and/or loading in urogynecologic surgeries. Such decreases in pore geometry support the hypothesis that regional increases in the concentration of mesh leads to an enhanced local foreign body response. Although pore deformation in transvaginal meshes requires further characterization, the findings presented here provide a mechanical understanding that can be used to recognize potential areas of concern for complex mesh geometries. Understanding mesh mechanics in response to surgical and...

Exploring the basic science of prolapse meshes

“…After exposing the transvaginal meshes Prolift and Prolift plus M (also known as Gynemesh and UltraPro or Artisyn) to relatively small loads, Otto et al [27] observed a loss of porosity in both the arms and central body of the mesh. In a further assessment of prolapse meshes loaded in a sacrocol-popexy model, Barone et al [23 ▪ ] saw similar results. When loaded to 5 N (1.1 lbs), Gynemesh PS, Alyte and UltraPro demonstrated a loss in porosity ranging from 2 to 87% and by 10 N most experienced a complete loss of porosity with virtually no pores ≥1 mm (Fig.…”

“…Furthermore, for some meshes (e.g. Gynemesh PS, Alyte, Restorelle, and UltraPro) structural properties are highly dependent on the direction in which the mesh is loaded [22,23 ▪ ]. These meshes are considered to be anisotropic – a property that is associated with the knit pattern of the mesh.…”

“…1). However, rotating the pores of Resorelle by 45°, a 90% reduction in porosity was observed [23 ▪ ]. Given the importance of pore size and porosity, the reduction in pore size (less than 1 mm), porosity, and effective porosity all potentially decrease the biocompatibility of synthetic mesh (Fig.…”

“…These behaviors are consistent with a markedly unstable geometry. In contrast, Restorelle (square pore) is stable, with minimal loss of porosity at 10 N [23 ▪ ]. Adapted with permission from [23 ▪ ].…”

The use of polymeric meshes for pelvic organ prolapse: Current concepts, challenges, and future perspectives

“…This is notable in a reduction of stiffness and ultimate tensile strength and a permanent increase in length (Ulrich, Edwards, Alexander, et al, 2016). Additionally, loading and implantation can change structural parameters (e.g., pore size) which compromise biocompatibility of the implant (Barone, Moalli, & Abramowitch, 2016).…”